Very good article and it actually works.
I have this question then phoenix.
How would you take that same approach and use an alternate port, 587 instead of 25 ?
This is important to the community I because although not recommended many ppl do use dynamic IPs to run simple servers. Once they get their Dynamic DNS stuff working they sure do.
Now we see many ISPs not allowing outbound email via port 25 unless you authenticate with the ISPs specific account. You end up with all the emails outbound being stacked in the deferred queue.
I can say personally, I've used that article to guide me and have had success until recently. My ISP adopted that policy and I had to use my ISP's login to make zimbra work. Changing the port from 25 to 587 didn't work. I saw in the logs that mail.server.tld without the port 587. I run my mail server so I also saw that no traffic ever came over to my actual outbound server from the zimbra server. I saw the message got deferred in zimbra.
As tated once I plugged in ISPs smtp info and authenticated, off all the emails went.
What say you or others

TIA